The proposed research is designed to further our understanding of the adhesive properties of parasites which enable them to colonize and survive in the host environment. Specifically, the mechanisms by which mycoplasma adhere to host cell surface membranes will be examined in detail. The work will begin with the purification of the binding sites from M. gallisepticum and M. pneumoniae responsible for attachment to sialic acid moieties on the host cell. A recently developed sensitive radioactive assay will be used in the purification procedure. The chemical, immunological, and binding properties of the purified binding sites will be investigated. Other mycoplasmas, which do not require sialic acid moieties on the host surface for attachment, will be examined for carbohydrate mediated binding mechanisms. Highly purified glycosidases and host cell surface glycoconjugates will be used as probes to elucidate the carbohydrate components on the host surface essential for attachment by the mycoplasma species. It is expected that the understanding of the attachment of mycoplasmas to host cell surface membranes will contribute to our understanding of the attachment schemes employed by virulent microorganisms as well as the normal bacterial flora of the gastrointestinal system.